1. Field
The present invention relates to a wireless resource allocation control system, road-side unit, wireless resource allocation control method and wireless resource allocation control program in which a road-side unit placed on a road allocates and releases a wireless resource to and from vehicle-mounted units, each of which is mounted in a vehicle, in a predetermined area in which a vehicle-mounted unit and the other vehicle-mounted unit use a wireless resource to communicate.
2. Description of the Related Art
Hitherto, in order to implement services for aiming improvement of security, improvement of efficiency of transportation and improvement of comfort, an Intelligent Transport System (ITS) has been known in which roads and vehicles are integrated. This system attempts to implement the services through road-to-vehicle communication, which is performed between a base station (road-side unit) placed on a road and a mobile station (or vehicle-mounted unit) mounted in a vehicle, and a vehicle-to-vehicle communication, which is performed between mobile stations, (refer to Japanese Laid-open Patent Publication No. 11-306490).
Those services adopt a synchronous time-division communication method performing road-to-vehicle communication through spot communication (ad hoc communication) only within a road-to-vehicle area, which is limited as a communication area, performing full-duplex communication using different frequencies between communication from a base station to a mobile station and communication from the mobile station to the base station. Further in this the full-duplex communication, a communication frame comprises time-dived fixed lengths called slot. The communication is performed between one base station and multiple mobile stations (refer to Japanese Unexamined Laid-open Patent Publication No. 2001-112059 and No. 2005-100231).
The communication employing the synchronous time-division communication method requires the allocation of a slot, which is a wireless resource, to a vehicle-mounted unit by a road-side unit. For example, as a method for allocating slots, a technology has been known in which a base station allocates a time slot to mobile stations in order of the time that they request communication (refer to Japanese Laid-open Patent Publication No. 2001-223660).
Since a base station allocates time slots to mobile stations in order of the time they request communication in the conventional technology, the allocation of time slots to mobile stations in order of the time they request communication may result in the problems of the cases where communication is disabled since no time slot is allocated to a mobile station that highly requires information within a service area or, conversely, a time slot is allocated to a mobile station that less requires the information within a service area, which waists wireless resources.